Bellows for hydraulic, hydropneumatic, or pneumatic piston-cylinder units

ABSTRACT

A bellows for hydraulic, hydropneumatic, or pneumatic piston-cylinder units, especially for vibration dampers or MacPherson strut units for motor vehicles, is located between the end of a piston rod and a cylinder, and covers the part of the piston rod which projects out from the cylinder to provide protection against dirt and/or damage. An interior space of the bellows undergoes a change in volume as a result of the relative movement of the piston and cylinder. The end area of the piston rod distal from the cylinder includes at least one flow connection leading to the interior of the bellows. The flow connection allows an incoming and/or outgoing flow of air. The end area of the piston rod, i.e., the end which passes through a mounting bearing connecting the piston-cylinder unit to the body of the vehicle, is provided with a flow connection connecting the interior space of the bellows to the atmosphere.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention pertains to a bellows for hydraulic,hydropneumatic, or pneumatic piston-cylinder units, especially forvibration dampers or MacPherson strut units for motor vehicles, whereinthe bellows is located between the end of the piston rod and thecylinder and covers the part of the piston rod which projects out fromthe cylinder to provide protection against dirt and/or damage. Theinterior space of the bellows undergoes a change in volume as a resultof the relative movement of the parts with respect to each other and atleast one flow connection leading to the interior of the bellows isprovided to allow an incoming and/or outgoing flow of air.

[0003] 2. Description of the Related Art

[0004] Bellows for piston-cylinder units are already known, for example,from German Patent Document DE 102 00 608 A1. In these cases, avibration damper or a MacPherson strut unit is provided with a bellowsfor protection against dirt and/or damage. As a result of the relativemovement between the piston rod and the cylinder, the interior of thebellows undergoes a change in volume, for which purpose an openingleading to the interior of the bellows is provided to allow air to enterand leave. Because the vibration dampers or MacPherson strut units areexposed in the wheel well of the vehicle to water spray and dirt, theuse of a bellows can protect the piston rod, but, according to the stateof the art, the disadvantage is that incoming air also arrives from thiswheel well, and the outgoing air terminates in it.

SUMMARY OF THE INVENTION

[0005] An object of the present invention is to provide an improvedbellows for hydraulic, hydropneumatic, or pneumatic piston-cylinderunits such that when air is drawn in as a result of the relativemovement of the bellows, only clean air is obtained, this beingaccomplished without any extra assembly work.

[0006] To accomplish this object, the end area of a piston rod, i.e.,the end that passes to the outside through the mounting bearingconnecting the piston-cylinder unit to the body of the vehicle, isprovided with a flow connection connecting the interior of the bellowsto the atmosphere.

[0007] The advantage of this solution is that the air enters and leavesthe bellows in the end area of the piston rod. Because the flowconnection passes through the mounting bearing, the air is drawn in fromoutside the wheel well of the vehicle. There is thus no fear of dirtyair being drawn in from this area.

[0008] The flow connection from inside the bellows to the atmosphere maycomprise a transverse bore in the end area of the piston rod leading tothe interior of the bellows and a longitudinal bore proceeding from thetransverse bore and opening to the atmosphere on the side of themounting bearing opposite the piston-cylinder unit. Because the flowconnection in the end area of the piston rod consists of a transversebore and a longitudinal bore proceeding from it, this longitudinal boreextending all the way to the end of the piston rod, the design is verysimple and therefore advantageous. Because the end area extends throughthe mounting bearing, the incoming air is drawn in from outside thewheel well.

[0009] The end area of the piston rod may be screwed to the attachmentbearing such that the flow connection passes through the screw joint.

[0010] The bellows may be sealed and held in place appropriately bymounting at least one end of the bellows in a positive or nonpositivemanner on the adjacent components.

[0011] Other objects and features of the present invention will becomeapparent from the following detailed description considered inconjunction with the accompanying drawings. It is to be understood,however, that the drawings are designed solely for purposes ofillustration and not as a definition of the limits of the invention, forwhich reference should be made to the appended claims. It should befurther understood that the drawings are not necessarily drawn to scaleand that, unless otherwise indicated, they are merely intended toconceptually illustrate the structures and procedures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In the drawings, wherein like reference characters denote similarelements throughout the several views:

[0013]FIG. 1 is a cross sectional view of the upper attachment end of apiston-cylinder unit according to an embodiment of the presentinvention;

[0014]FIG. 1a is a cross sectional view of an area where the bellows isattached to a mounting bearing according to another embodiment of thepresent invention;

[0015]FIG. 2 is a cross sectional view of the piston-cylinder unit ofFIG. 1 after the piston rod has traveled into the cylinder; and

[0016]FIG. 3 is a cross sectional view of another attachment of thebellows to the piston-cylinder unit.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0017] [0011] FIG. 1 shows a piston-cylinder unit 1 including acontainer tube 14 in which the individual parts (not shown in detail) ofthe vibration damper itself are located. A piston rod 2 projects outfrom this container tube 14, the upper end of the piston rod 2 extendingthrough an upper mounting bearing 3. The upper mounting bearing 3 isattached to the body of a vehicle, whereas the lower area of thepiston-cylinder unit with the piston rod 2 and the bellows 8 is locatedin a wheel well of the vehicle. A longitudinal bore 5 a of a flowconnection 5 in an upper end area of the piston rod 2 leads to the areaoutside the wheel well, e.g., to the area underneath the hood. Thelongitudinal bore 5 a is connected to the interior space 15 of thebellows 8 by a transverse bore 6. Air thus escapes the interior space 15of the bellows 8 to the outside via the transverse bore 6 and thelongitudinal bore 5 a of the flow connection 5, when the piston rod 2,as shown in FIG. 2, moves into the container tube 14 and the bellows 8is thus compressed.

[0018] [0012] The upper end area of the piston rod 2 is attached to themounting bearing 3 via a screw joint 4 with a nut 4 a. In the embodimentshown in FIG. 1, an upper attachment part 9 is clamped axially betweenthe mounting bearing 3 and the upper end area of the piston rod 2. Theupper attachment part 9 holds the bellows 8 in place. The opposite endof the bellows 8 is mounted in a lower attachment part 10 is arranged ata lower area of the piston rod 2, i.e., on the end of the container tube14 where the piston rod 2 enters the container tube 14.

[0019]FIG. 1a shows an embodiment in which the upper attachment part 9that holds the bellows 8 is formed directly on the inner end of themounting bearing 3, as an integral part of it.

[0020]FIG. 3 is an enlarged view showing the connection of the lower endof the bellows 8 to the lower attachment part 10. The bellows 8preferably consists of a rubber or rubbery material, such that thepretension of the bellows 8 allows it to rest with a sealing effectagainst an undercut area 11 of the lower attachment part 10. Thevibration damper or the MacPherson strut unit tends to corrode in theclosed off area of the container tube proximate the undercut area 11. Aradial extension 12 is provided on the bellows 8 to protect theendangered area from intruding moisture. The radial extension 12 of thebellows 8 is under pretension. If necessary, a small opening 13 may beprovided at the lowermost point of the bellows 8 to avoid theaccumulation of condensate, although the main venting function continuesto be performed via the flow connection 5.

[0021] Thus, while there have shown and described and pointed outfundamental novel features of the invention as applied to a preferredembodiment thereof, it will be understood that various omissions andsubstitutions and changes in the form and details of the devicesillustrated, and in their operation, may be made by those skilled in theart without departing from the spirit of the invention. For example, itis expressly intended that all combinations of those elements whichperform substantially the same function in substantially the same way toachieve the same results are within the scope of the invention.Moreover, it should be recognized that structures and/or elements shownand/or described in connection with any disclosed form or embodiment ofthe invention may be incorporated in any other disclosed or described orsuggested form or embodiment as a general matter of design choice. It isthe intention, therefore, to be limited only as indicated by the scopeof the claims appended hereto.

What is claimed is:
 1. A piston-cylinder unit comprising a cylinderhaving an open end and a piston rod movably inserted in said cylinderthrough said open end and having a distal end projecting out of saidcylinder, said distal end being insertable through a mounting bearingfor connecting the piston-cylinder unit to a support, and a bellowscovering a section of said piston rod projecting out of said cylinderfor protecting said section of said piston rod against at least one ofdirt and damage, wherein a flow connection is defined in said piston endin an area proximate said distal end of said piston rod, said flowconnection being in communication with an interior space defined in saidbellows and in communication with the atmosphere such that said flowconnection allows a flow of air between the atmosphere and said interiorspace when said interior space in said bellows undergoes a change involume in response to a relative movement between said piston andcylinder.
 2. The piston-cylinder unit of claim 1, wherein said flowconnection in said free distal end of said piston rod comprises atransverse bore leading to the interior space of said bellows and alongitudinal bore proceeding from said transverse bore and opening outat the distal end of said piston rod.
 3. The piston cylinder unit ofclaim 1, further comprising a mounting bearing for mounting the pistoncylinder unit to a vehicle body, said distal end area of said piston rodbeing threadably inserted in said mounting bearing forming a screwjoint, said flow connection extending through said screw joint.
 4. Thepiston cylinder unit of claim 1, wherein at least one end of the bellowsis mounted to said piston cylinder unit by a positive connection.
 5. Thepiston-cylinder unit of claim 1, wherein at least one end of the bellowsis mounted to said piston unit by a non-positive connection.
 6. Thepiston-cylinder unit of claim 1, wherein said piston-cylinder unit isone of a hydraulic, hydropneumatic, or pneumatic piston-cylinder unit.7. The piston cylinder unit of claim 1, wherein said piston-cylinderunit is one of a vibration damper and a MacPherson strut for a motorvehicle.
 8. The piston-cylinder unit of claim 7, further comprising amounting bearing for connecting the free distal end of said piston rodto a vehicle body, said free distal end of said piston rod passingoutward through said mounting bearing.